Intrusion-free physiological condition monitoring

ABSTRACT

A physiological well-being monitoring system especially suited for use by the pilot or other aircrew members of a high-performance aircraft such as a tactical aircraft is disclosed. The monitoring arrangement includes non-invasive sensing of arterial blood supply in the cranial adjacent portions of the pilot&#39;s body through the use of pulsating vascular bed optical signal transmission. The signal transmission is accomplished by way of sensors included in a pilot invisible and non-obstructing modification of, for example, the oxygen mask portion of the pilot life-support apparatus. Use of the physiological monitoring signals to generate alarm or assume control of the aircraft is also disclosed along with representative data associated with the sensed pilot physiological well-being indicators.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

BACKGROUND OF THE INVENTION

This invention relates to the field of non-intrusive, non-invasivephysiological monitoring of a human test subject and particularly to themonitoring of cranial region physiological conditions in the aircrewmembers of high performance aircraft.

G-force induced loss of consciousness (GLOC), an extreme example ofphysiological deterioration, has been found to be second only to thephenomenon of spatial disorientation in the priority of human factorsthreats facing aircrew members of a modern tactical aircraft. GLOC, infact, is believed to be one of the primary causes of present-daytactical aircrew fatalities notwithstanding the use of anti-G suits anda number of other human factor improvements in the modern fighteraircraft. Each increment of aircraft performance improvement since theearly 1900's has, in fact, been accompanied by an increased measure ofdanger from this source to aircrew members with the threshold of GLOChaving been crossed at least in the early 1920's or some 65 years ago.The U.S. military, particularly the U.S. Air Force and U.S. Navy, havebeen active in advancing the loss of consciousness prevention art as isexemplified, for example, by numerous issued patents relating toanti-G-force suits and other G-force threat minimizing apparatus. Themajor concern with which GLOC and other human stress problems areregarded in modern tactical aircraft is also exemplified by the reclinedseat, advanced anti-G suit servo valves, G limiting flight controlcomputer, and other human factors considerations that are standardequipment in the F-16 and other present-day tactical aircraft.

Notwithstanding these efforts, however, there has heretofore been anotable absence of satisfactory operational loss of consciousnessmonitoring arrangements for aircrew members. Principally, this absencearises because such monitoring has been considered to necessarilyinvolve the use of either anatomically invasive instrumentation devicesor at best, the use of dermal sensing electrodes. Such arrangements are,of course, highly disfavored or even considered to be physiologicallyand psychologically threatening by aircrew members.

To be acceptable in an aircraft operational environment, it is necessarythat the physiological condition monitoring arrangement be totallyinvisible o unobtrusive to an aircrew member. In addition to thisnon-interfering nature of practical GLOC monitoring equipment, themeaningful use of such equipment is, for example, to actuate an alarmsystem or activate an automatic pilot system and assume control of theaircraft. This demands that an employed GLOC system be both highlyreliable and impeccably accurate. Accuracy of this degree, for example,goes well beyond the bounds of sensing the G-force loading incurred bythe aircraft and its crew members. Such accuracy requires that real timeindividual responses of crew members, notwithstanding person to personvariations and variations in the physiological resilience of a givenperson from time to time be considered.

One of the more promising approaches to such improvement in the GLOC andphysiological monitoring of an aircrew member involves extension of theoximeter instrumentation commonly used in patient monitoring systems ina modern hospital into the arena of aircrew physiological monitoring. Afirst-blush consideration of this extension, however, incurs difficultywith a need for intimately placed and often, subjectively locatedanatomical sensors in the case of monitored hospital patients. Thisnecessity of intimate sensors for the hospital oximeter has, in fact,prompted the principal usage of such instrumentation to be withunconscious or severely movement restrained patients in the hospitalsetting. In one frequently used oximeter system, for example, thepresence of patient movement and the resulting spurious signals receivedat the oximeter has prompted the use of EKG related signals, (signalsderived from chest electrodes) as a timing trigger source to increaseoximeter reliability. Clearly, arrangements of this type are unsuitablefor use in an operational aircraft environment.

The usefulness of the oximeter instrument in a hospital setting isillustrated by a number of U.S. patents which relate to the oximeterinstrument. Included in these patents are several relating to the probeor transducer device used in collecting oximeter or physiologicalcondition signals from a person--e.g. the following patents: U.S. Pat.Nos. 4,770,179; 4,700,708; 4,685,464; 4,621,643; 4,167,331; 3,998,550;3,847,483; 3,704,706; 3,638,640.

In addition to these probe related patents, many of which are concernedwith the need for a low-cost disposable and sterile probe in thehospital environment, the patent art includes a number of documentsrelating to various aspects of the oximeter monitoring system ingeneral. Several of these patents describe the operating theory andother aspects of designing a practical oximeter instrument. Included inthese overall system documents are the following U.S. patents:

U.S. Pat. No. 4,714,341--"Multi-Wavelength Oximeter Having a Means forDisregarding a Poor Signal" issued to K. Hamaguri et al.

U.S. Pat. No. 4,653,498--"Pulse Oximeter Monitor" issued to W. New, Jr.et al.

U.S. Pat. No. 4,603,700--"Probe Monitoring System for Oximeter" issuedto R. A. Nichols et al.

U.S. Pat. No. 4,266,554--"Digital Oximeter" issued to K. S. Hamaguri etal.

U.S. Pat. No. 4,407,290--"Blood Constituent Measuring Device and Method"issued to S. A. Wilber.

U.S. Pat. No. 3,704,706--"Heart Rate and Respiratory Monitor" issued toP. R. Herczfeld et al.

U.S. Pat. No. 3,998,550--"Photoelectric Oximeter" issued to M. Koniskiet al.

U.S. Pat. No. 2,706,927--"Apparatus for Determining PercentageOxygen--Saturation of Blood" issued to E. H. Wood et al.

The disclosure of this group of overall oximeter system patents ishereby incorporated by reference into the present specification.

Notwithstanding these examples of inventive attention to oximeterrelated instruments, the patent art has failed to provide a satisfactoryoperational physiological monitoring system for the pilot or otheraircrew member of a high-performance aircraft.

SUMMARY OF THE INVENTION

In the present invention, the pilot of a tactical aircraft is providedwith a non-invasive and invisible cerebral region physiological statemonitoring arrangement that involves new optical sensing elementsdisposed in existing pilot life-support apparatus and coupled toelectronic processing circuitry of the type employed in state-of-the-arthospital patient oximetry processors.

It is an object of the present invention, therefore, to provide anon-invasive, invisible physiological monitor for a pilot or aircrewmember of a high-performance aircraft.

It is another object of the invention to provide a cranial regionphysiological monitoring arrangement which employs non-invasive opticalsensing of cranial region elements of a monitored person.

It is another object of the invention to provide cranial regionphysiological monitoring which employs sensing elements that aredisposed in existing pilot life-support apparatus.

It is another object of the invention to provide cranial regionphysiological monitoring sensors which employ solid-state energytransducers that are disposed in the oxygen mask of the monitoredaircrew member.

It is another object of the invention to provide a cranial regionphysiological monitoring arrangement which is based on sensing thecoloration and density variations of a pulsating vascular bed regionthat is disposed in the nose structure of a person.

It is another object of the invention to provide a cranial regionphysiological monitoring arrangement for a pilot which operates bysensing coloration differences between oxygenated and deoxygenatedhemoglobin.

It is another object of the invention to provide a physiologicalmonitoring apparatus that is responsive to the quantitative presence ofhemoglobin in an internal carotid artery connected pulsating vascularbed region of a monitored aircrew member.

It is another object of the invention to provide a physiologicalmonitoring apparatus which operates in response to circulatoryconditions in the nasal septal anterior ethmoid artery of a monitoredaircrew member.

It is another object of the invention to provide a physiological statemonitoring arrangement in which physiological sensing signal conductorscan be combined with existing communication conductors in a commontether cable that is of minimal encumbrance to an aircraft pilot

It is another object of the invention to provide a pilot physiologicalmonitoring arrangement that employs a two spectral frequency opticalmonitoring of a pulsating vascular bed region in the pilot.

It is another object of the invention to provide a physiologicalmonitoring system which may be used for detecting loss of consciousness,mental impairment and other physiological disability conditions in anaircraft pilot.

It is another object of the invention to provide a physiologicalmonitoring arrangement which generates a signal that may be combinedwith additional physiological signals to generate a verifiedphysiological danger signal.

Additional objects and features of the invention will be understood fromthe following description and the accompanying drawings.

These and other objects of the invention are achieved by aviationlife-support apparatus comprising the combination of a facial maskmember receivable over the nose and lower facial region including themouth and nose apertures of a human test subject; means forcommunicating a flow of oxygen inclusive breathing gases to and fromsaid mask member and said human test subject; acoustic to electricaltransducer means received in said mask member in acoustic communicationwith said human test subject for generating electrical signalsrepresentative of test subject generated vocal sounds; optical sensingmeans received in said mask member and in optical communication with afacial region pulsating vascular bed of said test subject for sensingG-force influenced quantitative blood flow indicators in said vascularbed and the adjacent cerebral regions of said test subject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an aircraft pilot and pilot life-support apparatus whichincludes physiological monitoring in accordance with the invention.

FIG. 2 shows additional details of physiological monitoring sensors fromFIG. 1 and adjacent life-support apparatus.

FIG. 3 shows a physiological monitoring system block diagram inaccordance with the invention.

FIG. 4 shows the effect of G-force acceleration on a physiologicalindicator that is subject to monitoring with the invention.

FIG. 5 shows the effect of G-force on a plurality of human physiologicalindicators.

DETAILED DESCRIPTION

At 100 in FIG. 1 is shown the head portion of an aircraft crew membersuch as a pilot together with the helmet 102 and oxygen mask 106portions of the life-support system used by such pilots in tactical andother military aircraft. In the FIG. 1 drawing, the pilot's helmet 102is shown to include a sun visor 104 and a receptacle 114 by which theoxygen mask 106 is held in place over the nose and mouth portions of thepilot's face. Connecting with the receptacle 114 and a similar not shownreceptacle on the opposite side of the helmet 102 are a pair of springloaded bayonet connectors 110 and 112 to which are attached an array ofadjustable webbing members 108 that connect with the mask 106 andprovide adjustable tension for holding the mask in position over thepilot's face.

In the U.S. military, it is common practice to mold masks of the typeshown at 106 in FIG. 1 to the unique facial features of each user pilot.This custom molding together with the flexible conforming nature of theinterior liner 134 portion of the mask 106 enables the array ofadjustable webbing members 108 in FIG. 1 to be capable of holding themask 106 in both a fixed predetermined position and in a relativelyimmovable position with respect to the pilot's facial features. Thisproperty of the mask 106 lends especially well to the present inventionadditional capabilities or improvements provided for the mask 106.

Additional details of the improved mask 106 which are shown in FIG. 1include an audio signal to electrical signal transducer or microphone136 which is disposed in close proximity with the pilot's mouth when themask 106 is positioned over his face. Also shown in FIG. 1 is theflexible conduit or hose 126 by which oxygen and/or other life-supportgases are communicated to the mask 106 and the pilot 100 from sources inthe Piloted aircraft. The multiple conductor electrical cable 128 andits attached multiple pin connector serve to connect both the microphone136 and the physiological state monitoring elements of the invention toelectronic circuit apparatus mounted in the aircraft.

The improved mask 106 in FIG. 1 also includes a plurality of elementsassociated with the physiological monitoring system of the presentinvention. Among these elements are the apertures 118 and 120 which aredisposed in opposed portions of the nose bridge region of the maskinterior liner 134. In this arrangement, the apertures 118 and 120located on opposite sides of the upper nose bridge region or the nasalseptal anterior ethmoid artery region 116 of the pilot 100 when the mask106 is worn. By way of the apertures 118 and 120, the nose bridge region116 of the pilot 100 is exposed to optical signals originating in one ormore electrical to optical transducer devices received in one of theapertures 118 and 120. This nose bridge region is also examined orsensed with an optical to electrical transducer generator of electricalsignals that is disposed in the opposite of the apertures 118 and 120.

In both FIG. 1 and FIG. 2 of the drawings, a pair of such transducers isshown in both the aperture 118 and the aperture 120 and in the cutawayregion 216 of FIG. 2. These transducers are identified with the numbers132 and 134 for the aperture 118 in FIG. 1 and with the numbers 138 and140 in the aperture 120. A more comprehensive view of such transducersappears in the cutaway portion 216 of FIG. 2 with the transducers beingindicated by the numbers 210, 212, 226 and 228 in the view of FIG. 2.

Electrical lead wires for the transducers 132 and 133 are shown at 121and 122 in FIG. 1 and the similar lead wires for transducers 138 and 140are shown at 123 and 124 in FIG. 1. The lead wires 121-124 in FIG. 1 arecombined into the multiple conductor electrical cable 128 which alsocommunicates microphone and headphone signals. In FIG. 2, the leads fromthe transducers 210, 212, 226 and 228 are combined into a multipleconductor cable 208 which is maintained in separation from themicrophone transducer and headphone transducer cables 204 and 205. Themicrophone and headphone leads in FIG. 2 are combined into the separatemultiple conductor cable 206 for connection to the aircraftcommunications system.

According to the present invention, it is contemplated that one pair ofthe transducers in the apertures 118 and 120 of FIG. 1 function aselectrical energy to optical energy converting or transducing deviceswhile the oppositely disposed pair of transducers serve as opticalenergy to electrical energy converting transducers. By way of thisarrangement, density and coloration variations in the optical signalpath traversing the pilot's upper nose bridge region are determinativeof an electrical signal which is generated by the optical energ toelectrical energy group of transducers. This electrical signal, in turn,can be processed into signals which define a number of pilotphysiological well-being indicators.

The theoretical aspects of physiological well-being indicators whichmonitor percentage of hemoglobin molecules saturated with oxygen, pulserate, pulse waveform, pulse amplitude and pulse absence to gain insightinto the physiological state of a human subject are described in theherein incorporated by reference oximeter patents and are additionallydescribed in the list of publications included in the appendix hereof.The U.S. Pat. No. 2,706,927 of Wood et al in the above incorporated byreference group is especially enlightening in this regard. For presentpurposes, it is sufficient, however, to note that usable physiologicalsignals can be obtained from a pulsating vascular bed located in thenasal septal anterior ethmoid artery region of the pilot 100 through theuse of two color responding electrical to optical signal transducers inthe apertures of FIG. 1.

For example, the transducers 132 and 133 in the aperture 118 can be madecapable of generating two spectrally separated optical signals--signalsof, for example, 660 nanometers and 920 nanometers wavelength, (in thered and infrared portion of the electromagnetic spectrum) by employingsilicon light emitting diodes as the transducers 132 and 133.Transducers of this type are, for example, found capable of providingelectrical output signals from the oppositely disposed optical toelectrical transducers, the transducers 138 and 140 in FIG. 1, thatdistinguish between the presence and absence of bright red oxygenationin the hemoglobin reaching the pilot's nasal region 116. Such signalscan also measure the amount of oxygenated hemoglobin reaching the nasalregion 116 and can accomplish this measurement during each instant offlight and G-force exposure.

The red and infrared nature of the optical signals generated by lightemitting diode embodiments of transducers 132 and 133 can be understoodto generate differential amplitude responses in the optical toelectrical transducers 138 and 140 in accordance with the amount of redor blue coloration, that is, the amount of oxygenation in the blood ofthe pilot 100. It is especially desirable that in the FIG. 1arrangement, this measurement of red or blue coloration and oxygenatedblood presence can be accomplished in the cranial adjacent pulsatingvascular bed region indicated at 116 in FIG. 1.

In a related manner, optical signals from the region 116 of the pilot100 are also capable of indicating both the absence of blood flowpulsations in the brain adjacent portions of the pilot and of indicatingthe quantitative amount or amplitude of these pulsations. The absence ofpulsations in the region 116, of course, indicates a blacked-out or GLOCcondition in the pilot or the ensuance of a condition in which pulseamplitude degradation and spectral shifts in oxygenated blood predictloss of judgment and other mental functions. The optical to electricalsignal transducers 138 and 140 in FIG. 1 may be embodied in the form ofsilicon solar cells or other preferably solid state optical toelectrical transducer devices having spectral responses that arecompatible with the selected electrical to optical transducer devices.

The upper nose bridge region of the pilot 100, that is the nasal septalanterior ethmoid artery region 116, is found to be especially desirablefor use in monitoring decreased blood flow in an aircraft pilot that issubject to downwardly directed or +Gz acceleration--that is toaccelerations which tend to push the pilot more firmly into his seat.Such acceleration forces tend to diminish blood flow to the cerebral orcranial region of the pilot and to include a diminishing of the bloodpressure and flow in the carotid artery system which supplies the brain.

The close proximity of the pulsating vascular bed in the nasal septalanterior ethmoid artery region of a human to the carotid artery is foundto provide a desirable degree of tight coupling or direct relationshipbetween carotid presence and flow conditions and the conditions sensedin the vascular bed--a relationship that is useful for the presentphysiological monitoring apparatus. Moreover, the short time delaybetween carotid artery pressure and flow and pressure and flow in theethmoid artery region is also desirable for the present invention.Therefore, the pulsations and density and coloration variations sensedin the pulsating vascular bed of the nasal septal anterior ethmoidartery region 116 provide an unusually desirable basis for physiologicalmonitoring.

It is also clear that other regions of a pilot's face or head could beemployed for G-force influenced physiological monitoring--especiallyother regions which may be served by sensors under the oxygen mask 106or similar pilot life-support apparatus.

Within the oximeter apparatus which receives optical-electrical signalsfrom the region 116 of the pilot 100, a measurement taken in the absenceof the pilot's pulse is compared with a measurement taken in thepresence of a pulse. This arrangement allows for correction of factorssuch as the presence of venous blood and tissue in the sensed pulsatingvascular bed. Two optical wavelengths are used in the sensing for suchinstruments in order to calculate the oxygen saturation of arterialblood. The ratio of the absorptions at the two sensing wavelengths is ameasure of the percentage of hemoglobin saturation in the illuminatedblood. Additional details regarding these measurements are to be foundin the above incorporated by reference patents.

Before leaving the FIG. 1 and FIG. 2 drawings, certain of the thereinillustrated details are deserving of comment. The oxygen mask shown inFIG. 1 and FIG. 2 is of the P12 type currently used by the U.S. AirForce and other U.S. military. The mask is comprised of a molded hardplastic body member, indicated at 222 in FIG. 2, to which is attachedthe soft and pliable interior lining portions of the mask--the portionswhich are resilient and face mating and indicated at 224 in FIG. 2. Themask shown in FIG. 1 and FIG. 2 is fabricated inter alia by GentecCorporation using the assembly number 60240, and the identificationnumbers G012-1050-04, however, the invention is not limited to the useof this or any other mask or life-support apparatus.

The apertures 118 and 120 in the mask 106 may, of course, be molded orcut into the nose covering portion of the mask interior liner 134 withthe transducers 132, 133, 138 and 140 being received in molded pocketsof the interior liner. In small quantity and experimental use thesetransducers may be attached with materials such as silicon rubber orrubber cement or other attachment arrangements as are known in theresilient material arts. Other arrangements of the apertures 118 and 120and the transducers, arrangements such as covering the apertures withprotective and optical signal transmitting media are, of course,possible and are to be recommended in large quantity fabrications anduses of the invention.

The cutaway portion 216 of the mask in FIG. 2 shows how either theinterior surface of the mask liner 134 or a cloth like supplementaryelement 220 may be used to mount the transducers 210, 212, 226 and 228.A supplementary element of this type is supplied as a portion of theNellcor D-25 oxisensor array that is preferred for use in embodying theinvention.

The elements 200 and 202 which are shown attached to the molded plasticbody portion of the FIG. 2 mask are actually portions of the microphone136 which appears in FIG. 1. The element 202 in FIG. 2 is a removableelectrical connector for the microphone signal conductors of the cable206. The cable 205 connects with the pilot's earphone set. In a morerefined version of the FIG. 2 mask, the optical transducer electricalsignals of the cable 208 could, of course, be brought out through theelements 200 or 200 and 202 to maximize the degree of pilot conveniencein using the FIG. 1 and FIG. 2 apparatus. FIG. 1, in fact, shows the useof a single multiple pin connector for both the audio and optical signalfunctions of the mask 106. In the FIG. 2 arrangement of the invention,the optical transducer electrical conductors of the cable 208 are shownto be passed through a sealed aperture region 218 of the plastic bodymember 222. The small recessed area and protruding button indicated at214 in the element 200 of FIG. 2 serves as a release latch for theelement 202.

The mask 106 of FIG. 1 and FIG. 2 is regarded as a relativelyshort-lived and frequently replaced item of pilot support apparatus inview of its lightweight, resilient and therefore physically vulnerablenature; the disposable nature of the oximeter sensing transducersdescribed in the above recited probe or oximeter sensor patents areconveniently compatible with this disposable nature of the mask 106. Ina fully operational arrangement of the FIG. 1 and FIG. 2 mask, thedisposable nature of the optical transducer elements therefore adds onlya limited degree of cost to the overall mask assembly.

FIG. 3 in the drawing shows a block diagram of a system which employsthe optical physiological monitoring sensors of FIG. 1 and FIG. 2. InFIG. 3, a group of four transducers 304, 305, 306, and 308 are showndisposed on opposite sides of the upper bridge portion of the pilot'snose 300. The FIG. 3 transducers are held in relative position by asubstrate member 302 and the mask of FIGS. 1 and 2 which is not shown inthe FIG. 3 view. Alternately, the substrate member 302 can be held inposition by an elastic band 328 passing behind the head of the pilot orother monitored subject. Such an elastic band support arrangement isespecially desirable for mask-free physiological monitoring uses of theinvention outside the aviation art--as a supplement to the previouslydiscussed hospital monitoring sensor arrangements, for example.

The transmitter and receiver nature of the transducers of substrate 302together with the previously identified optical spectral regionpreferred for use in the FIG. 3 apparatus are indicated at 310 in FIG. 3with the indication at 310 suggesting that only one receiver thetransducer 304 is used. Signals to and from the transducers in FIG. 3are conveyed by the multiple conductor cable 312 in communication withthe oximeter instrument of block 314. The oximeter 314 may be of thetype described in one or more of the above incorporated by referencepatents or an instrument manufactured by one of the forty or soinstrument suppliers that are currently active in this field.Instruments manufactured by Hewlett Packard Corporation of the SanFrancisco peninsula region of California or the Nellcor Co. Inc. ofHayward, Calif. are useful at 314 in FIG. 3; the Nellcor N-200 oximeteris preferred. Alternately the oximeter 314 may be of a largely softwareembodiment as is suggested in the above incorporated by referencepatents.

The output signals available from an oximeter of the indicated type areindicated at 316, 318, 320, 322 and 324 in FIG. 3. The nature of thesesignals is well-known in the medical instrumentation art and is furtherdescribed in connection with the test subject related data in FIG. 4 andFIG. 5 herein. Use of one or more of the signals 316-324 to actuate aphysiological state related apparatus such is an automatic pilot isindicated at 326 in FIG. 3. It is the intent of the present inventionthat one or more of the signals 216-324 be used as at least a vote in adecision arrangement which ultimately decides that a monitoredcrewmember such as a pilot is not in a safe physiological condition. Analarm condition or replacement of the pilot's function by an automaticpilot as indicated in FIG. 3 is therefore the ultimate possible use ofinformation generated by the present apparatus. The exact nature of thesignals available from an oximeter instrument is also described in theabove incorporated by reference patents and in other prior artpublications including the references recited in the appendix hereof.

In the FIG. 3 system, a pair of optical energy to electrical energytransducers are shown. This two transducer arrangement is in keepingwith the parallel connected receiver transducers in the FIG. 1 and FIG.2 representations of the invention. In each of the FIGS. 1, 2 and 3instances, it is intended that the receiver transducer be of the broadoptical spectrum type notwithstanding the use of electrical to opticaltransducer illumination sources that are of the limited spectral outputtype. The use of electrically parallel connected dual received devicesas in FIGS. 1 and 2 and in an arrangement where each receiver isresponsive to the optical energy signal originating in both opticalenergy sources has been found to be desirable when movement or slippageof the transducers on the monitored subject can occur. Two receives alsoincrease the area of reception for the transmitted signals.

The use of a single receiver transducer is found to be acceptable aslong as a pilot's mask 106 does not slip excessively in an accelerationenvironment of the system. Such movement would, of course, move thetransmitter/receiver transducers out of a alignment with the upper nosebridge region 116. It is possible that some other number of receiver andtransmitter transducers other than the herein described one and twodevices may be most practical for a fully optimized embodiment of theinvention.

During optical energy transmission through tissue such as the pulsatingvascular bed of the upper nose bridge region 116, as indicated in FIG. 1and FIG. 3 of the drawings, the diffusing effect of the vascular bedtissue precludes the tendency for energy from one optical source to bereceived principally by one receiver transducer device. Each of the tworeceiver devices in FIGS. 1, 2, and 3 is therefore responsive to theoptical energy output of each of the sources, the sources at 132 and133, for example. The transducer redundance and the additional activetransducing area provided by the two receiver arrangement of FIGS. 1 and2 are additionally desirable from both the reliability and signalenhancement viewpoints.

The optical spectrum wavelengths indicated at 310 in FIG. 3 are found tobe satisfactory from both the oxygenated and deoxygenated hemoglobinspectral absorption viewpoint and additionally for convenience ofoptical energy generation with low cost and readily available solidstate transducers devices. It is, of course, also possible to generateoptical energy of the indicated wavelengths using a broad spectrumsource such as an incandescent lamp together with appropriate filtering.Optical signals of other spectral frequencies may be desirable inalternate embodiments of the invention and can be achieved withappropriate filters and a broad spectrum source or with solid stateelectrical to optical transducers having outputs in a selected differentportion of the optical spectrum.

FIG. 4 in the drawing shows the correlation between G-force environmentand one of the principal physiological well-being indicators that issubject to monitoring with the present invention. The FIG. 4 drawingrepresents a time record of a simulated aerial combat maneuver in whichthe pilot of an F-16 aircraft, for example, is subjected to 120 secondsof combat maneuvering G-forces including two peaks of seven G amplitudeand peaks of five and six G amplitude. The G-force environment in FIG. 4is indicated by the curve 400 which is used in conjunction with thevertical scale 408. During the interval represented by the curves ofFIG. 4, the human test subject is reclined in an F-16 like seat with a30° seat back angle and is exerting the customary anti-G strainingmaneuver.

The data of FIG. 4 graphically illustrates the concept proposed byauthor Barr, in the appendix cited 1962 investigation, that decreases inarterial oxygen saturation, result from increasing G-force. The Barrinvestigation also focuses on the susceptibility of lung function in ahuman test subject to changes in G-force environment. Otherinvestigators, including the appendix cited work of Nolan et al in 1963,have found that oximetry measurements taken about the head of a humantest subject, do in fact, accurately track cuvette oximetry measurementsobtained from blood continuously withdrawn from a radial artery duringexposures to accelerations in the 2 to 5 G-range.

One effect of the G-force environment represented by the curve 400 inFIG. 4 is indicated by the curve 402 which is read in conjunction withthe vertical scale of percent saturated oxygen at 406. Several aspectsof the oxygen saturation curve 402 are notable including the significantfall of percent oxygen saturation from the 95% region to the 86% regionfollowing initial onset of a 7 G-force peak. Continued falling of thepercent oxygen saturation with intervals of mild recovery during periodsof lower G-force and progression to saturation levels in the 80% regionare indicated by the latter portions of the curve 402. The delayeddirect correlation between G-force magnitude and oxygen saturation isespecially notable in the FIG. 4 curve.

The significance of the curve 402 in FIG. 4 can be even betterappreciated with the understanding that, generally, saturated oxygenpercentages in the 70 to 80% range result in notable losses of cognitivemental ability in a human test subject. Saturation values lower than 82%moreover result in significant mistakes on the part of a test subjectand values below 70% are considered an extreme cut off for pilot safety.The operating environment of the present invention is further defined bythe generally accepted notion that only three to five seconds ofconsciousness remain for an aircrew member once a lack of pulseconditions occurs in the carotid artery region.

The notable decrease in hemoglobin oxygen saturation indicated in FIG. 4has been attributed to a combination of effects including decrease inheart pumping volume, particularly in the end-diastolic volume, strokevolume, and cardiac output. This decrease is also attributed to collapseof the pulmonary alveoli during G-force acceleration; to arterial venousshunting in independent regions of the lungs and to unfavorable effectsresulting from G-suit force action on the diaphragm of a human testsubject, see the appendix cited work of Vanderberg et al. The data ofFIG. 4 represents a composite of the results obtained from eight AirForce volunteers of an average 27 years of age while wearing the U.S.Air Force issued CSU 13/P anti-G suit and breathing atmospheric air byway of an unconnected oxygen mask distal connector.

FIG. 5 in the drawings shows additional response characteristics of ahuman test subject to the sudden onset of a G-force pulse, the data ofFIG. 5 includes respiration volume as indicated at 506 and measuredalong the scale 514; hemoglobin oxygen saturation as indicated by thecurve 504 and measured along the scale 512; heart rate as indicated bythe curve 502 and measured along the scale 510 and the G-force pulse asindicated by the curve 500. The lower axis 508 in FIG. 5 indicates timein increments of one minute. Tidal volume, an indication of ventilationefficiency is included at 518 in FIG. 5 with the scale at 516 measuringsuch tidal volume.

The FIG. 5 drawing confirms the disruptive effect of G-forces onarterial oxygen saturation as well as on respiratory volume and heartrate. Of particular additional significance in the FIG. 5 drawing is theextreme drop in the curve 504 which occurs during and after the +5 gpeak shown in curve 500. This interaction between increasing G anddecreasing percent arterial oxygen saturation demonstrates theimportance of monitoring the physiologic state of the pilot in highperformance aircraft.

The data of FIGS. 4 and 5 indicates the influence of G-force incurred inthe positive Z direction, that is force tending to urge a pilot morefirmly into his seat, on readily measured clinical indications ofphysiological well being. In a sense therefor, the data of FIGS. 4 and 5indicate the need for systems of the type herein described and alsoindicate the range of sensitivities and data variables to be expected asinput signals by systems of this type.

The effects and results disclosed in FIGS. 4 and 5 are, however, relatedto only one of the possible factors making use of non-invasivephysiological monitoring of tactical aircrew members desirable. Inaddition to the G-force incidents represented in FIGS. 4 and 5, a numberof other physiological well-being threats frequently are encountered bya tactical aircraft crew member. These other events can include the lossof life-support systems, e.g., the loss of oxygen due to equipmentfailure or combat damage, and the loss of G-suit operation.Additionally, these threats can include such effects as hyperventilationin which the pilot is subjected to excessive levels of oxygen andbecomes involved in a vicious circle sequence of exertion and oxygensaturation that leads to his inability to function.

The monitoring system of the present invention is capable of initiatingenvironmental changes in response to any or a combination of thesethreatening conditions in a pilot in view of its precise monitoring ofthe ultimate results of the undesirable condition. The presentlydescribed monitoring of the quantitative amount of oxygen present in thecirculatory system of a pilot and the accomplishing of this monitoringat a point that is closely connected with the pilot's brain represents anearly ideal monitoring arrangement. It is also desirable that thismonitoring is accomplished in a non-invasive and invisible to the pilotmanner. The signals developed by the present optical sensing of apulsating vascular bed can, of course, be combined with other signalswhich indicate a deterioration of physiological condition in apilot--signals such as eye blink sensing, hand grip on control stickmeasurement, head slump detection, EEG indications and incurred G-forcemagnitude. Signals of this nature may be combined with the outputsignals of the present system to provide a correlated or verifiedphysiological condition indicating signal.

The present invention therefore provides an electrode free non-invasiveand desirably located sensor arrangement for sensing informativeparameters relating to the physiological well-being of a pilot or otherpersons. The described system has been found capable of functioning evenin the extreme conditions of 9 G_(z) acceleration force and is found toprovide results which correlate with invasive arterial sampling of testsubjects undergoing G-force or other environmental conditions. The brainproximity of the region sensed by the present monitoring system isespecially desirable with respect to time delay considerations andaccuracy.

Appendix

The following publications in the field of human test subjectphysiological monitoring are believed to be of interest with respect tothe background of the present invention. Certain of the publicationsherein listed have been discussed in the preceding text.

Barr, P. Hypoxemia in man induced by prolonged acceleration. ActaPhysiol. Scand. 54:128-37, 1962.

Crosbie, R. J. A Servo Controlled Rapid Response Anti G-Valve, NADC,Warminster, PA, 1983 SAFE Meeting, Las Vegas, Nev., 6-8 December 82.

Dhenin, G., Effects of long duration acceleration, Aviation Medicine,Trimed Books Limited; London, 1978.

Jennings, T., Seaworth, J., Howell, L., Tripp, L., Ratino, D., andGoodyear, C. The Effect of +Gz Acceleration on Cardiac VolumesDetermined by Two-Dimensional Echocardiography. SAFE Journal, WinterQtr, 1985, Vol 15, No. 4.

Lindberg, E., Sutterer, H., Marshall, R., Headly, R. and Wood, E. 1960.Measurement of Cardiac Output during Headward Acceleration Using the DyeDilution Technique, Aerospace Medicine, 31: 817-834, 1960.

Mackenzie, N. Comparison of pulse oximeter with an ear oximeter and anin-vitro oximeter, J. of Clin Monitoring, vol. 1, pp. 156-160, July 85.

New, W. 1985. Pulse Oximetry, J. of Clin Monitoring, vol. 1, No. 2,April.

Nolan, A. C., Marshall H. W., Cronin, L., Sutterer, W. F., Wood, E. H.Decreases in arterial oxygen saturation and associated changes inPressures and Roentgenographic appearance of the Thorax during forward(G_(x)) acceleration. Aerospace Med. 1963; 34: 797-813.

Vanderberg, R. A., Nolan, A. C., Reed, J. H., Wood, E. H. Regionalpulmonary arterial-venous shunting caused by gravitational and inertialforces. J. Appl. Physiol. 1968; 25:516-27.

Yelderman, M., New, W., Evaluation of Pulse Oximetry. Anesthesiology,October, 83: Vol 59, No. 4, pp 349-352.

Yoshiva, I., Shimadan, U., Tanoha, K. Spectrophotometric Monitoring ofarterial oxygen saturation in the fingertip. Med Biol Eng Comput 1980;18:27-32.

While the apparatus and method herein described constitute a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus or method, and thatchanges may be made therein without departing from the scope of theinvention, which is defined in the appended claims.

We claim:
 1. Aviation life support apparatus comprising the combinationof:a facial communications and oxygen delivery mask member receivableover the nose and lower facial region of an aircrew member; opticalsensing means received in said mask member and in optical communicationwith a nasal septum region pulsating vascular bed of said aircrew memberfor sensing G-force loading influenced quantitative blood flowindicators in said vascular bed and adjacent cerebral regions of saidaircrew member.
 2. The apparatus of claim 1 wherein said pulsatingvascular bed includes a nasal septal anterior ethmoid artery region ofsaid aircrew member.
 3. The apparatus of claim 1 wherein said opticalsensing means includes solid state electrical to optical and optical toelectrical signal transducers coupled via optical signal passing throughsaid pulsating vascular bed.
 4. The apparatus of claim 3 wherein saidelectrical to optical signal transducers include a plurality of lightemitting diode transducer elements each generating an optical signal ofdifferent optical wavelength.
 5. The apparatus of claim 4 wherein saiddifferent optical wavelengths are selected in response to the opticalenergy absorption characteristics of hemoglobin.
 6. The apparatus ofclaim 3 wherein said facial mask member includes means closely conformedto facial features of said aircrew member for quickly disposing saidmask in the same relative facial position during each usethereof;whereby consistent and comprehensible electrical signals aregenerated by said optical sensing means.
 7. The apparatus of claim 6wherein said facial mask member is custom mold fitted to the facialfeatures of each individual aircrew member.
 8. The apparatus of claim 3wherein said mask member includes acoustic communications transducermeans and wherein electrical signals attending said electrical tooptical and said optical to electrical signal transducers and saidacoustic transducer means are communicated from said aircrew member tothe surrounding environment via a common tether.
 9. The apparatus ofclaim 5 wherein said electrical to optical signal transducers includeseparate transducer elements generating optical energy at thewavelengths of six hundred sixty and nine hundred twenty nanometers. 10.Physiological condition monitoring apparatus for a exposed aircrewmember comprising the combination of:a mask member disposed in coveringrelationship over at least the nosebridge facial region of said aircrewmember; a source of optical energy radiation mounted on said mask memberin a first nosebridge facing position thereon; optical-to-electricalenergy transducer means mounted on said member in an opposed secondnosebridge facing position thereon, for generating electrical signalsrepresenting optical energy signals received from said source of opticalenergy radiation via blood encolored tissue in the nosebridge region ofsaid G-force exposed aircrew member; and oximeter means for convertingsaid transducer means electrical signals into physiological conditionrelated electrical signals for said G-force exposed aircrew member. 11.The apparatus of claim 10 wherein said source of optical energyradiation and said optical-to-electrical transducer means are receivedon opposed lateral surfaces of said mask and thereby reside adjacentopposed lateral nose surfaces of said aircrew member while said mask isreceived in said nosebridge covering relationship.
 12. The apparatus ofclaim 11 wherein said source of optical energy radiation has opticalenergy output in the red to infrared spectral region.
 13. The apparatusof claim 12 wherein said optical-to-electrical energy transducer meansincludes a plurality of optical-to-electrical transducer elements andsaid elements are each selectively responsive to energy in a differentred to infrared optical spectrum portion.
 14. The method of monitoringblood oxygen content in an oxygen mask assisted person comprising thesteps of:illuminating nasal septum facial regions of said person withoxygen mask nose region sourced optical energy of predetermined red toinfrared spectral band energy content; collecting, with oxygen mask noseregion located optical-to-electrical signal transducer means, a sampleof the optical energy transmitted through blood encolored said nasalseptum region tissue of said person; and converting the transducingmeans electrical signals into physiological condition related electricalsignals using a red, and infrared, spectral region dual spectral bandoximeter conversion.
 15. Oxygen mask apparatus comprising thecombination of:a facial feature conformed enclosure member receivableadjacent nose and mouth structure openings of an oxygen-assisted person,said enclosure member including first and second surface portionsextending one along each side of said nose structure of said assistedperson; means for communicating a flow of life-supporting oxygeninclusive gases to and from the space within said enclosure member andthereby to and from said assisted person; a source of opticalillumination mounted on said first surface portion of said enclosuremember and directed toward an adjacent lateral nose surface of saidassisted person; and optical signals reception means mounted on saidenclosure member second surface portion and responsive to the opticalillumination signals originating in said source of optical illuminationand passed through nose region blood encolored tissue of said person.